Field of the Invention
This invention generally relates to gels having tacky surfaces and, more specifically, to surface treatments which will render the gel tack-free.
Discussion of Related Art
A “gel” is often defined as a semisolid condition of a precipitated or coagulated colloid. Within this definition, gels can differ widely. On one end of the spectrum gels are more fluid in nature but have some solid properties. An example of such a gel might be a gel toothpaste. At the opposite end of the spectrum, the gels are considered solids with some fluid properties.
It is toward this end of the spectrum that gels are commonly used to facilitate load distribution. Gels enhance this function by offering a high degree of compliance which basically increases the amount of area available to support a load. With an increased area of support, the load is accommodated at a considerably reduced pressure. Particularly where the human body is involved, a reduced pressure is desirable in order to maintain capillary blood flow in body tissue. It is with this in mind that gels are commonly used for bicycle seats, wrist pads, insole supports, as well as elbow and shoulder pads.
While the advantageous properties of gels have made them candidates for many applications, one disadvantage has seriously limited their use. Most gels are extremely tacky. This characteristic alone makes them difficult to manufacture and aggravating to use.
Attempts have been made to produce gels that are naturally non-tacky. But such attempts unfortunately have resulted in an intolerable sacrifice of the advantageous properties. Attempts have been made to enclose the gels in a non-tacky pouch. This has also tended to mask the advantageous properties and to significantly increase manufacturing costs. Powders and lubricants have been applied to the tacky surfaces with results limited in both duration and effect.
Gels have also been of particular interest in the formation of seals where the high compliance and extensive elongation of the gel are of considerable value. Such is the case with seals used in trocars and other surgical access devices, where a seal must be formed both in the presence of a surgical instrument and in the absence of a surgical instrument.
In general, a trocar is a surgical device intended to provide tubular access for surgical instruments across a body wall, such as the abdominal wall, and into a body cavity, such as the abdominal cavity. Often, the body cavity is pressurized with a gas, typically carbon dioxide, to enlarge the operative volume of the working environment. Under these conditions, the trocar must include appropriate seals to inhibit loss of the pressurizing gas through the trocar. Thus, a zero seal must be provided to seal the working channel of the trocar in the absence of the instrument, and an instrument seal must be provided to seal the working channel in the presence of the instrument.
Most recently, both zero seals and instrument seals have been provided by a pair of rollers disposed on opposing sides of the working channel. The rollers have been formed of a gel material providing a high degree of compliance, significant tear strength and exceptional elongation. As noted, however, the best gel materials tend to exhibit surfaces that are very tacky. The use of a tacky gel can make the processes of manufacturing and using the gel seals extremely difficult. The disadvantages are increasing in this application, where a tacky gel also produces significant drag forces during instrument insertion. Furthermore, the tacky surfaces tend to draw and retain particulate matter during the manufacturing and handling processes. For these reasons it has been even more desirable to render the highly tacky gel surfaces non-tacky in the case of medical devices such as trocars.
Many attempts have been made to facilitate handling the rollers during manufacture and to lower instrument drag forces during use. For example, use of lubricants such as silicone oil, KY jelly, and Astroglide, have been applied to the surface to reduce tackiness. Unfortunately, these lubricants tend to dry out over time leaving the gel in its natural tacky state. Non-tacky gels have also been investigated. The non-tacky gels, however, are not particularly heat tolerant, as low amounts of heat can rapidly cause the materials to take a set and distort particularly under compressive loads. This can occur over an extended period of time, for example, even at normal room temperatures.